Method of treating metallic surfaces



Patented Dec. 22, 1931 UNITED STATES PATENT OFFICE sumtm REDWAY MASON, OF WEMEITE, ILLINOIS, A SSIG-NOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., CORPORATION OF NEW YORK METHOD OF TREATING METALLIC SURFACES No Drawing.

This invention relates to a method of treating metallic surfaces, and more particularly to a method of coating sherardized surfaces to improve their appearance.

On account of the dark color of sherardized surfaces, they are not suitable for exposed parts where appearance is of importance, which fact has in the past limited the thin-coating of cadmium on the sherardized surfaces. Y

The invention will be more fully understood from the following description. In the practice of the invention a bath is formed, the grleferred constituents and vproportions of w 'ch are as follows:

Water 250 c. c. NaCN 60 g. NaOH g.

, The proportions of the above ingredients may be considerably varied, depending upon the nature of the work to be finished, the thickness of cadmium coatin desired, and 5 various other factors, as will apparent to those skilled in this art. It will also be obvious to those skilled in the art that certain substitutions may be made in the ingredients listed above. Thus, instead of cadmium cara 40 bonate, the chloride or other salt may be used;

instead of the sodium cyanide; potassium or other cyanide ma be used; or cadmium cyanidema be use to take the place of all of o the cadmium carbonate and a part of the sodium cyanide.

Application filed September 12, 1928. Serial No. 805,618.

The bath being preferably at a temperature of about 80 0., the sherardized parts are introduced therein by any suitable dipping means, and kept in the solution for, one minute or such time as is found b experience to be suflicient to produce the esired coating. No external electromotive force need be applied, since the zinc, being above cadmium in the electromotive series, will displace the cadmium from the solution, forn'i- -ing an even electrolytic deposit of cadmium. E

-This treatment forms a pleasing white 1 coating on the parts which greatly improves" their appearance, and at the same time in creases the rust-proofing effect of the zinc.

Because of the fact that no electromotive force need be applied, the process may be carried out veryeconomically.

What is claimed is:

A method of brightening a sherardized surface, which consists in immersing the surface for about one minute in a bath containing the follo 'ng ingredients in substantially the fo owing proportions; water, 250

cubic centimeters; sodium cyanide,v s;. sodium hydroxide, 30 grams; and c o ium j carbonate, 10 grams; he temperature of the bath bein substantial y 80 (1, thereby causing the eposition of a thin layer of cadmium upon the surface without the imposition of an external electromotive force.

In witness whereof, I hereunto subscribe my name this 27th day of August,A. D. 1928.

, SUMNER REDWAY MASON. 

